Biomedical subjects

Derek Dunn-Rankin

Publications and source records attributed to Derek Dunn-Rankin.

3 recordsLinked to original sources

PubMed2006

Using large electric fields to control transport in microgravity.

Transport control by large electric fields in microgravity may be subdivided according to whether the charge carriers are flame ions, ions produced by corona discharges, or electrically charged particles. Using electric fields to induce and direct convection through the drag exercised on neutral gas by ions and to manipulate dispersions and trajectories of electrically charged droplets and particles is especially effective in the absence of Earth's gravity. We have explored applications associated with each of these, and this review collects and summarizes briefly the principal findings of our research, which is scattered widely over the literature of combustion, electrostatics, and experimental science.

Journal Article↗

PubMed2003

Temperature field measurements of small, nonpremixed flames with use of an Abel inversion of holographic interferograms.

Interferometry has been used for many years as a semi-quantitative image-based diagnostic for combustion research. In this paper, we use image-plane, double-pulse holographic interferograms of axisymmetric flames to infer their radial temperature distribution. An Abel inversion is performed on the fringe data to account for line-of-sight integration through the flame. The sensitivity of nonresonant refractive diagnostics decreases inversely with temperature, and the accuracy of the technique is discussed in this context. A small, nonpremixed capillary flame is investigated, and the temperatures inferred from interferometry are compared with those obtained with N2 coherent anti-Stokes Raman spectroscopy thermometry. Additionally, the thermal field of a burning monodisperse methanol droplet stream is investigated interferometrically. Because of their small size, both of these flames challenge the performance limit of temperature interferometery.

Journal Article↗

PubMed2003

Crossed two-beam coherent anti-stokes Raman spectroscopy in dispersive media.

Coherent anti-Stokes Raman spectroscopy (CARS) is a nonlinear optical wave mixing process that is used in gas-phase systems to determine the energy distribution of the probed species (usually N2) and, through a fitting procedure, the temperature giving rise to it. CARS signal strengths are maximized when the phase matching condition is met. Because gases are generally non-dispersive, this phase matching condition can be found geometrically as a function of the crossing angles between the CARS beams and their wavelengths. In addition, perfect phase matching in non-dispersive media occurs automatically for collinear beams. To improve spatial resolution, however, intersecting the laser beams is desirable. Being a third-order process, phase matching for CARS in gases typically requires three input laser beams. This paper discusses and demonstrates the issues of phase matching for CARS when the medium is dispersive, and the ability for CARS phase matching to occur with only two crossed laser beams (one pump and one probe). This two-beam X-CARS in dispersive media can be used as an alignment tool for gas-phase CARS and may be relevant as a simpler diagnostic in high-pressure environments. The paper also discusses the effects of non-ideal phase matching in dispersive and non-dispersive media.

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